Breast Imaging Techniques for Breast Cancer: Section 2.b.

CONTENTS:

2.4 Conventional (Diagnostic) Mammography
2.5 ‘Surveillance’ Mammography
2.6 Some New Developments in Mammography
2.6.1 Digital Mammography
2.6.2 Computer-Aided Detection (CAD)
2.6.3 Tomosynthesis or ‘3-D’ Mammography
2.6.4 Stereoscopic Digital Mammography
2.6.5 Scintimammography
2.6.6 Positron Emission Tomography (PET)
2.7  Breast Ultrasound
2.7.1 Indications for Breast Ultrasound in Screening
2.7.2 The Role of Diagnostic Breast Ultrasound

Forward to 2C on Abnormal mammo and MRI Back to 2A on screening

Hey, be nice to me. I’m one step away from being rich, all I need now is money.

2.4: Breast Imaging: Conventional (Diagnostic) Mammography

If a breast abnormality is present on clinical examination then a diagnostic mammogram is necessary.  During a diagnostic mammogram samples are taken for cytology or histopathology.

The diagnostic mammogram is usually supervised by a Radiologist and the views obtained adapted to evaluate any specific abnormality.  In addition, an ultrasound may be necessary. Magnification views may provide details of breast calcification and the margins of any masses.

So, you find a lump, you go to your doctor and he sends you for a mammogram.

Yes, that would be a diagnostic mammogram.

A focal ‘spot compression’ view is performed by applying focal compression to the area of interest in the breast, using a small compression paddle.

Additional views, such as anterior compression or an exaggerated cranio-caudal (XCC) view may be necessary to maximize imaging of as much breast tissue as possible.

Using a 90-degree lateral view of the breast, the X-ray beam can travel from either the medial (medio-lateral) or from the lateral (latero-medial) side of the breast.  The lateral view is a direct orthogonal view to the cranio-caudal (CC) projection and is useful in triangulating breast lesions.

Oh my goodness! I think you have to be a radiologist to understand that bit.

Well I understand up to the X-ray beam bit…

Just keep calm and Beam on.

More Mammographic Views of the Breast

The best mammographic view to evaluate breast calcifications is a ‘delayed lateral’ view.  To obtain this view, the breast can be in compression for up to two minutes. This view can confirm the presence of benign patterns of breast calcification or with benign breast micro-cysts.

Tangential views can further evaluate a palpable mass or confirm breast calcification.

Remember, radiologists can see things in you that other people can’t.

‘Rolled’ CC views can help to confirm that the three-dimensional nature of a finding seen only on one of the conventional views.  The technologist places her hands on either side of the breast and ‘rolls’ the breast tissue, medial and lateral for the CC view; superior and inferior for the MLO view.  The technician compresses and rolls the breast tissue, to obtain the image. This imaging method may also assist the subsequent performance of an accurate targeted ultrasound to sample the cells or tissue of the lesion.

Breast compression improves image quality. Oral or topical analgesics and cushioned paddles may minimize discomfort during compression.

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2.5 ‘Surveillance’ Mammography

Surveillance mammograms are performed for women who have a history of breast cancer.   So, for five years follow-up screening is necessary, after a diagnosis of breast cancer.  Surveillance mammograms are  similar to diagnostic mammograms.  So, there is  a radiologist on-site who can interpret the study and determine if further views or tests will be necessary.

If the patient does not develop recurrence within the first five years, the patient returns to routine screening for subsequent years.

How often would you have a mammogram after breast cancer treatment?

Typically, you would have a mammogram yearly for five years, although it does depend on your treatment center.

2.6 Some New Developments in Mammography

The breast cancer screening program has played a role in accelerating the development of new imaging refinements and techniques that improve detection and diagnosis of breast disease. A summary of some of the key imaging developments is below:-

2.6.1 Digital Mammography

When compared to standard ‘film’ mammography, ‘full field’ digital mammography can improve image quality and assist study interpretation, but it is more costly.

I’m getting lost very early here, What is digital mammogragphy?

Digital mammography uses digital receptors and computers instead of X-ray film to examine breast tissue for abnormalities.

Now don’t get me wrong, I like fields, especially full ones, I just don’t see their place in this case.

So far, digital mammography has not demonstrated a significant impact on cancer detection rates. Standard film mammography remains an acceptable breast screening modality for all women.

2.6.2 Computer-Aided Detection (CAD)

Computer-aided detection (CAD) may improve the sensitivity of mammographic screening but has not been demonstrated to reduce mortality rates from breast cancer. CAD may increase patient recall rates.

2.6.3 Tomosynthesis or ‘3-D’ Mammography

In 2012, breast tomosynthesis (also known as ‘3-D’ mammography) has been approved by the US Food and Drug Administration (FDA) for routine diagnostic clinical use as an adjunct to standard mammography.

Tomosynthesis is a modification of digital mammography; it uses a moving x-ray source and a digital detector.  The radiologist acquires and reconstructs a three-dimensional volume of data, using a computer algorithm.  Next, the computer generates thin ‘sections’ of images.  Thin ‘slice’ reconstruction improves the image of a breast lesion in the slice because it eliminates overlap from surrounding breast tissues and structures.

A breast imaging examination using tomosynthesis has a slightly longer exposure time for each image, which lasts at least 10 seconds, in comparison to standard digital mammography.  However, disadvantages of this breast imaging exam is that the radiation dose per image is higher and there can also be motion artifacts.

‘Motion Artifacts’ they sound like something out of an Indiana Jones movie.

Motion artifacts occur as a result of movement during the scan, this can result in blurring or ‘ghosting’ on the image.

I’m shaking with fear now, he said ghost. I’m phasmophobic you know?.

A paper by Friedewald and colleagues, published in October 2014, has reviewed the role of tomosynthesis in breast cancer screening. These authors have claimed that the:

“Addition of tomosynthesis to digital mammography was associated
with a decrease in recall rate and an increase in cancer detection rate”.

To truly evaluate the use of tomosynthesis in breast cancer screening,  further research studies are necessary.

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Figure 2.3  

A standard mammogram (CC view) (Left) compared with
a 3-D tomography image (Right) showing a small tumor.
(From, Grady, D. New York Times, June 24^th 2014).

2.6.4 Stereoscopic Digital Mammography

Stereoscopic digital mammography is currently a research technique; it involves using a stereoscopic viewer to view two full-field digital mammographic images, taken at a slight angle from each other. In this way, the technique can visualize ‘depth’ in internal breast structures. The radiation dose is twice that for standard imaging.

2.6.5 Scintimammography

‘Nuclear medicine breast imaging’ or scintimammography may be necessary after an initial screening or diagnostic mammogram.

Scintimammography uses a radioactive atom, ‘technetium 99’ (Tc-99m) which is attached to a molecule called ‘Sestamibi.’ Sometimes the procedure is simply called a ‘mibi scan.’ The Sestamibi molecule is taken-up by metabolically active tissue, such as rapidly dividing cancer cells, and may, therefore, reveal an otherwise hidden lesion.

Scintimammography involves injecting a radioactive dye into the patient. The dye will accumulate differently in cancerous versus non-cancerous tissues and can help determine whether cancer is present.

Scintimammography, sounds Scintillating, but what exactly is it?

Very simply, an injection into the vein of a radioactive tracer that attaches to cancer cells. The cancerous cells then show up on imaging.

Wow! That is very cool!

This technique is helpful for women who have particularly dense breast tissue, for women with breast implants, or when multiple tumors are suspected. The technique can also help differentiate between possible tumors and scar tissue from a previous mastectomy.

Sometimes, if there is already a definite breast cancer diagnosis, scintimammography can be a useful imaging method to help with the ‘staging’ technique.

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Breast Imaging: Benefits of Scintimammography

For a primary breast lesion of greater than 1 cm, scintimammography has an estimated sensitivity of 85%, specificity of 89%, a positive predictive value of 89%, and a negative predictive value of 84%.  The sensitivity for detection of axillary node metastasis is about 77%, with a specificity of about 89%.

Although radiologists consider mammography to be the best tool for breast cancer screening,  scintimammography also has certain benefits.

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Figure 2.4 

Scintimammographic image shows a central
breast mass.

From a patient’s perspective, perhaps the greatest benefit is the immediacy of the results. It is not necessary to wait for a six to twelve months follow-up.  Scintimammography tends to be useful when there is a palpable lesion greater than 1cm in diameter.  A confirmed negative reading via scintimammography can, therefore, be quite reassuring.  A nuclelar medicine specialist performs and reads scintimammography images, rather than radiologist.

It is only possible to get a scintimammogram in a hospital or setting which has a nuclear medicine department.

Well that’s great news because waiting for the results is often the worst part of any tests.

Yes, I agree. I often find myself waiting….for cake… for waffles… for pancakes..I could go on.

2.6.6   Positron Emission Tomography (PET)

Also, nuclear medicine specialists interpret PET scans because an injection of radioactive dye is necessary. Thus, the specialist measures the ‘uptake‘ of the dye as it passes through different parts of the body.

A PET scan is used to scan the ‘whole body‘, and is sometimes used as part of breast cancer ‘staging’ to check for metastasis of the cancer to other parts of the body.

PET scans measure changes in metabolic rate, and as cancer cells have a slightly higher metabolic rate than other cells, it will show ‘hot spots‘ of increased density where malignant cancer masses are likely to be developing.

Figure 2.5 Positron emission tomogram (PET)

of the breast, shows a ‘hot spot’ of metabolically
active tumor cells.

Normally, a PET scan is not the breast imaging method of choice for breast cancer screening.   However, PET scans may be useful as part of the differential diagnostic process, or when deciding whether a biopsy of a breast abnormality is necessary.

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…a jaguar in her garage, a tiger in her bed….

…..and a Jackass to pay for it all!

An advantage of the use of breast PET scans in the breast cancer screening process is that it avoids the use of invasive procedures.  However, the down side of PET scans are additional costs and an increase in exposure to radiation.

A new technique called ‘positron emission mammography’ (PEM) utilizes a high-resolution imaging technique that gives a lower rate of false positives than breast MRI.  But it is unlikely that PEM will gain broad acceptance unless it proves to reduce costs and give additional time-saving and life-saving information, not available to the other imaging techniques.

2.7 Breast Ultrasound

Ultrasound imaging uses high frequency sound waves to form an image, called a ‘sonogram’.  The sound waves it uses are harmless and pass through the breast and bounce back or ‘echo‘ from various tissues to form a picture of the internal structures.

An unexpected ‘echo‘ means that there is a solid nodule of some kind within the tissue.  An ultrasound uses no radiation, thus, for pregnant women, it is the diagnostic breast imaging method of choice.

Breast ultrasonography has distinctive roles in diagnosis of detected breast abnormalities and in screening to detect early breast cancer.

Figure 2.6  Breast ultrasound

of a post-surgical breast mass
(black on the ultrasound).
The image cannot distinguish
between surgical scar
and recurrent tumor.

2.7.1 Indications for Breast Ultrasound in Screening

The addition of breast ultrasound to mammographic screening has yet to be shown to reduce breast cancer mortality.  At the present time, there have been no clinical trials that compare screening for breast cancer with combination ultrasound and mammography and mammography alone.

One of the most important roles of breast ultrasound is in the diagnostic follow-up of an abnormal screening mammogram.

Ultrasound can differentiate a solid mass from a cyst and also can  evaluate breast masses or breast asymmetries. Color  Doppler ultrasound can also aid in the assessment of breast masses.

What is the difference between an ultrasound and ultrasonography?

Don’t worry, they’re the same exam.

EXAM!!! Did somebody just say Exam? Is there an exam on this?

The addition of ultrasonography to mammography decreases specificity for breast cancer diagnosis but increases the sensitivity for small breast cancers.

A large multi-center, prospective clinical trial was conducted through the American College of Radiology Imaging Network (ACRIN Protocol 6666). ACRIN concluded that adding screening ultrasound to mammography can identify an additional 4.3 cancers per 1000 women screened. The ACRIN study also showed an increase in the number of false-positive results (positive predictive value for mammogram alone 22.6 % versus 11.2 % for mammogram plus ultrasound). Other multi-center trials have reported similar findings (Berg et al., 2008).

I used to be indecisive, but now I’m not so sure.

The American College of Radiology states that:

“the addition of ultrasound to screening mammography
may be useful for incremental cancer detection” (Lee et al., 2010).

2.7.2 The Role of Diagnostic Breast Ultrasound

Breast ultrasonography is used to provide guidance for biopsy procedures, fine needle aspiration (FNA) cytology and other interventions when a breast abnormality has been identified.

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Breast ultrasound has the following additional diagnostic roles:

• Ultrasound is the first-line breast imaging method when a woman is pregnant or less than 30 years old and she has focal breast symptoms or findings;
• In addition, ultrasound is helpful in evaluating the local extent of breast cancer;
• Ultrasound can identify additional tumor in the same breast when mammography has detected the main tumor mass.
• Ultrasound is used to evaluate the axilla and axillary lymph nodes in the setting of a newly-diagnosed breast cancer or when there are ‘suspicious’ finding on mammography.

When axillary ultrasound is positive, the suspicious lymph nodes may have an image-guided biopsy (FNA cytology or core biopsy) to confirm or exclude malignancy. A ‘positive’ axillary lymph node leads to full surgical axillary lymph node dissection, rather than sentinel lymph node (SLN) biopsy at the time of definitive breast surgery.

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References:

Friedewald, S.M., Rafferty, E.A., Rose, S.L., et al. (2014). Breast Cancer Screening Using Tomosynthesis in Combination with Digital Mammography. JAMA 311(24), 2499-507. (Retrieved October 28^th 2014): https://www.ncbi.nlm.nih.gov/pubmed/25058084

Berg, W.A. (2004). Supplemental screening sonography in dense breasts. Radiol Clin North Am. 42(5), 845-51. (Retrieved October 28^th 2014): https://www.ncbi.nlm.nih.gov/pubmed/15337420

More references for this section are on this page.

Patient Information:

American Cancer Society. For Women Facing a Breast Biopsy: Benign breast conditions: Not all lumps are cancer (Retrieved January 26^th 2015) http://www.cancer.org/treatment/understandingyourdiagnosis/examsandtestdescriptions/forwomenfacingabreastbiopsy/breast-biopsy-benign-breast-conditions

National Cancer Institute.Mammograms (Retrieved January 26^th 2015) http://www.cancer.gov/cancertopics/factsheet/detection/mammograms

More patient information for this section is on this page.

Forward to 2C on Abnormal mammo and MRI. Back to 2A on screening.